Systems and methods of payment by bank card are known. Generally the holder of the bank card must have a bank account and very often pay a subscription, and such systems or methods require a high level of security in order to combat numerous attempts at fraud.
The document EP0979495 B1 indicates a process of the prior art in which a chip card reader adds the amount of a purchase made by means of a card to a total of purchases made by previous purchasers so as to transmit to a bank, for example at the end of the day, this total, which represents a credit to the vendor. To remedy certain types of fraud, the aforementioned document recommends an execution of enciphering algorithms in the chip card by means of a private key and a public key. To make such a system less fragile vis-à-vis fraudsters, the authors prefer to add complications such as a public key certification.
The document WO 01/18756 discloses an electronic purse immediately rechargeable at a point of sale, which is represented by the existence of a second balance at the bank card. The reprovisioning at the point of sale can be offered only on a card back to back with a bank account.
The document WO 03/027919 presents a data processing installation for an electronic purse in which a communication device comprises a so-called “local account” memory so as to transfer data representing a local sum. The communication means are required by the existence of a distant account.
In the light of the aforementioned documents, the centralization and complexity of cryptographic devices seem inevitable in order to ensure that payments by means of electronic devices are made satisfactorily. This is not satisfactory in terms of flexibility and ease of use.
In order to dispense with the need for transactions with a bank, the document FR2827058 discloses a payment system for an electronic purse by means of which a payment is made by deducting a purchase amount from the amount remaining in the memory of the electronic purse. An operation of recharging the electronic purse from a payment terminal avoids the rejection of a purse with a precharged amount when the balance is exhausted.
The latter solution also has certain drawbacks such as the potentiality of fraudulent recharging unless inevitably complex cryptographic devices are used or at least an available or recharging amount is limited. The inconveniences should also be noted that can result from unavailability of the physical medium for the purse when going to a shop through reasons of theft, loss, loan to a friend or to another member of the family, or purely and simply by forgetting.